Method and an apparatus for separating a segmentation medium from a stream of a segmented main fluid

ABSTRACT

Segmented main fluid in a capillary stream is allowed to flow through a main tubing equipped with a capillary slot communicating with an offtake pipe. Conditions within the apparatus are maintained such that capillary forces and surface tension inherent in the elements of the segmentation medium and other parts of the system prevent their passage through the capillary slot, through which the main fluid only is taken off in a continuous stream. The length of the capillary slot in the direction of the main capillary tubing axis exceeds the maximum contact length of a segmentation medium element; the main fluid may be taken off substantially from a single one only, or from not more than two neighboring segments of the main medium, so that contamination by the contents of other segments is negligible.

United States Patent Hrdina [54] METHOD AND AN APPARATUS FOR SEPARATING A SEGMENTATION MEDIUM FROM A STREAM OF A SEGMENTED MAIN FLUID [72] Inventor:

[73] Assignee:

.liri Hrdina, Prague, Czechoslovakia Ceskoslovenska Czechoslovakia 22 Filed: Sept. 15,1969

21 Appl.No.: 857,956

akademie, Prague,

[30] Foreign Application Priority Data Sept. 19, 1968 Czechoslovakia ..657l/68 [56] References Cited UNITED STATES PATENTS Buchtel ...55/197 Feb. 8, 1972 Primary ExaminerCharles N. Hart Attorney-Paul H. Smolka [57] ABSTRACT Segmented main fluid in a capillary stream is allowed to flow through a main tubing equipped with a capillary slot communicating with an offtake pipe. Conditions within the apparatus are maintained such that capillary forces and surface tension inherent in the elements of the segmentation medium and other parts of the system prevent their passage through the capillary slot, through which the main fluid only is taken off in a continuous stream. The length of the capillary slot in the direction of the main capillary tubing axis exceeds the maximum contact length of a segmentation medium element; the main fluid may be taken off substantially from a single one only, or from not more than two neighboring segments of the main medium, so that contamination by the contents of other segments is negligible.

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JIRI HRDWA ATTORNEY METHOD AND AN APPARATUS FOR SEPARATING A SEGMENTATION MEDIUM FROM A STREAM OF A SEGMENTED MAIN FLUID BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to a method of and an apparatus for removing a segmentation medium from a segmented stream of a main fluid. A segmented stream is produced by dividing a main fluid passing through a tubing into individual segments, which are separated from one another by so-called segmentation elements, consisting either of bubbles or drops of so-called segmentation medium, which is substantially immiscible with the main fluid.

It is a known measure in the art to convert a continuous stream of a main fluid to be treated in a desired manner, e.g., measured, analyzed etc., into a segmented stream; considerable advantages are thereby achieved, if the stream of the fluid has to be passed through various appliances, such as analyzers comprising capillary reactors, dialyzers connecting tubes and the like. The segmentation elements are highly effective in preventing the intermingling of various segments of the main fluid, which usually contain different substances, such as samples-originally fully separated from one anotherto be successively analyzed in automatic analyzers. A segmented stream can further be used in processes, where a reduction of concentration gradients of various substances is to be obviated. This is the case for instance in chromatography, where various substances are conveyed by a stream of an eluent discharged from a chromatographic column, after they have been separated in the latter. The stream, entraining the various separated components of the original mixture (e.g., after the above-mentioned chromatographic separation), is passed through a number of appliances, such as capillary reactors, in which the reaction capillary has a considerable length in order to provide for the required period of reaction, further through a variety of hydraulic switches, mixers, connecting tubes etc. It is a great advantage, in particular in connection with automatic analyzers, that the segmentation elements efficiently prevent the intermingling of the fluid contained in the individual segments of the segmented stream, even if the fluid is passed through numerous appliances along a relatively long path.

"Before the main fluid is fed into the measuring or other treating apparatus, it has, as a rule, to be free from the segmentation medium, which, if admitted to the measuring or other apparatus (such as a flow photometer, colorimeter, flow conductometer etc.), would interfere with its operation.

The segmentation medium may consist of a gas, such as air, nitrogen or the like, and in this case the segmentation elements are constituted by gas bubbles or it may consist of mercury, oil or the like, in which case the segmentation elements consist of drops of a segmentation medium. With a view to the fact that the invention enables the use of any desired segmentation medium, either gaseous or liquid, the term segmentation elements will throughout this disclosure denote bubbles of gas as well as drops of liquid.

2. Description of the Prior Art Devices have previously been proposed for use in separating a segmenting medium from a stream of main fluid. In the majority of such known devices gas is used as the segmentation medium and as gas bubbles have to be removed from the main fluid stream, such devices have been called debubblers.

The heretofore known and used debubblers consist usually of a straight main tube or of a tube relatively sharply bent at the debubbling point, said main tube communicating with a branch line serving for the withdrawal of the main fluid, freed from bubbles. The branch line opens into the (sharply) bent or straight portion of the main tube by a funnel-shaped enlarged space, having a relatively large volume. The cross-sectional area by which the funnel-shaped space opens into the main tube has usually substantially equal longitudinal and transverse dimensions, which as to their order correspond approximately to the inner diameter of the main tube. Having reached this funnel-shaped space, the gas bubble finds here sufficient room to assume a shape determined substantially by its surface tension only, so that it can assume approximately a spherical shape (naturally slightly deformed by outer influences to which it is subject at this point). The bubble thus sets partially free the flow of the main fluid into the branch line, not only from the main fluid segment lying beyond the bubble, but also in front of the bubble.

If, under these circumstances, a reliable separating efiect is to be achieved, in order to remove the segmentation medium, the total through-flow profile at the point where the branch line opens into the main tube, must have such a size that the segmentation element (bubble), when passing through this point, should not close the through-flow profile at this point not even after it has changed its shape due to the release of forces, which previously acted thereon; when passing through this point, the dimension of the bubble in longitudinal direction is reduced but in transverse direction increased. The liquid can be taken off continuously from the lower part of the funnel-shaped space, without the gas bubble penetrating into the lateral takeofi' tube. However these devices show a considerable disadvantage in that in the relatively large funnelshaped space there occurs an intermingling of liquids not only from two adjacent segments but also from further segments of the segmented main fluid. In other words, the funnel-shaped space represents a relatively large pocket, in which an undesirable mixing of liquids from a plurality of segments takes place. This results in a highly objectionable reduction of the concentration gradients in the stream of the main fluid.

This is true even in spite of the fact that such devices are disclosed in various publications and patent specifications, where they are usually represented diagrammatically by a lateral tube, branching off from a main tube at right angles or under an inclination, without said funnel-shaped separating space being illustrated in the respective drawings. Such a device without a separating space, would, of course, be inoperative and incapable of achieving a reliable and perfect separation of the segmentation medium.

SUMMARY OF THE INVENTION The main object of the invention is to provide a method and an apparatus which are well adapted to effect a reliable elimination of the segmentation medium from the stream of a segmented main fluid.

Another object is to provide a method and an apparatus of the aforementioned type, which are adapted to remove elements of the segmentation medium intervening between the various segments of the main fluid, while substantially preventing the intermingling of more than two adjacent segments of the main fluid.

Still another object is to provide a method and an apparatus of the aforementioned type, which ensure a minimum depreciation of the concentration gradients in the stream of the main fluid.

A further object of the invention is to provide a method and an apparatus of the above type, which are universally applicable not only with a gaseous but also with a liquid segmentation medium.

A still further object is to provide an apparatus capable of operation in any required position and not only in a substantially vertical position, as is usual in the heretofore known devices.

Another object is to provide an apparatus of the aforementioned type, which can be produced without difl'lculties and at low cost, while ensuring a high accuracy in operation.

A further object is to provide an apparatus of the aforementioned type, which in combination with a measuring or other instrument enables a considerable increase in the accuracy of measurement or other treatment.

Other objects and advantages of the invention will be understood from the ensuing description of the invention considered in connection with the accompanying illustrative drawings.

The invention is based on a known phenomenon concerning the surface tension of a drop or bubble of a medium, surrounded by another medium with which it does not mix. As known, the surface tension acts on the drop of liquid in inward direction in such a way, that if no outer influence were present, the drop would assume theoretically the smallest volume confined in the surface of equal curvature i.e., a spherical shape. However, the drop is subject to outer influences, such as gravity, pressure, wall influence etc., which tend to deform it, but this is counteracted by the surface tension generating a certain resistance. If the drop lies against an aperture which is smaller than the diameter of the drop and if a pressure acts on the other side of the drop, the latter does not enter the aperture, as long as the resistance offered by the surface tension to the deformation of the drop, exceeds the outer pressure. The drop will just be more deformed, in dependence on the increasing outer pressure, and slightly penetrate into the aperture, but it will not pass through it. Not until the outer pressure increases to such a value as to overcome the resistance produced by the surface tension against a deformation of the drop to a dimension corresponding to the dimension of the aperture, will the drop be urged into the aperture. The value of the resistance against deformation (produced by the effect of the surface tension and capillary forces) at this moment will in the further disclosure be termed critical resistance against deformation."

The value of this resistance will depend on the nature of the material of the drop (and of the materials surrounding the drop), on the ratio between the drop diameter and the area of the aperture into which it has to be pressed, on the angle under which it penetrates into the aperture (the drop will enter easier into a conical aperture than into an aperture with sharp edges) on the characteristics of the material in which the aperture is made and in particular on the contact angle under which the respective meniscus bears on the wall etc. The value of the resistance may be determined without great difficulty for any given case. The drop or bubble when flowing through a tubing contacts the wall of the tubing along a certain length which likewise depends on outer influences, pressures, etc. This length will in the following specification be called contact length.

A further important factor is the afi'mity between the segmentation medium and the wall of the tubing, through which the segmentation medium advances. This affinity depends on the character of the medium and of the material of the wall of the tubing and is different for various substances. So is for instance the affinity between glass and mercury different from the afi'rnity between glass and water (or oil). This affinity, which plays an important role in the present invention, will hereinafter be called surface affinity of the segmentation medium."

The present invention utilizes the above-disclosed phenomenon for separating the segmentation medium (either a gas bubble or a drop of liquid) from the stream of the main fluid. The main inventive idea resides therein that from the segmented stream of the main fluid a capillary stream of said fluid is tapped along a path exceeding the maximum contact length of a segmentation element in the direction of flow of the segmented stream and this tapped stream, containing a part of the main fluid is taken off, while the outer influences acting on the segmentation elements and caused mainly by hydrostatic and hydrodynamic pressures, pressure difference at the transition from the main segmented stream, into the tapped stream and the takeoff pressure of the main fluid are maintained at a value lower than the critical resistance against deformation of "the segmentation element, exerted by the capillary effects, surface tension thereof and the surface affinity of the segmentation medium.

As a result, the segmentation element is not forced into the tapped stream, while a continuous takeoff of the main fluid from points directly in front of, and behind, the segmentation element or from a single segment of the main fluid is effected, the tapped main fluid being completely freed from segmentation elements, which will advance further with the segmented stream of the remaining main fluid to the waste or to further use.

By a suitable choice of the length of the tapped stream it may be achieved that the main fluid is taken off from not more than two adjacent segments of the main fluid and mostly from not more than one single segment, which fact contributes exceedingly to an increased accuracy and reduces the undesirable intermingling and contamination of different segments of the main fluid. I

The capillary tapped stream can be either continuous or may consist of several partial streams, whose overall length, measured in the direction of movement of the segmented stream is chosen such as to ensure the tapping of the main fluid from not more than two adjacent sections of the segmented main fluid.

Sometimes it is not of primary importance to tap samples of the main fluid from a single segment or from not more than two neighboring segments, greater emphasis being placed on a certain degree of smoothing or levelling the differences in quality of the individual segments or on a high flow rate of samples withdrawn from the segmented stream. In these cases the length of the capillary takeoff stream may be increased so as to extend over more than two segments.

The invention relates equally to an apparatus for efl'ecfing the new method. Such an apparatus comprises a main tubing for the stream of the segmented main fluid and a branch line for taking off (or sucking off) the main fluid freed from segmentation elements. According to the basic feature of the present invention the main tubing is provided with a capillary slot, connected over the branch line to takeoff means for the main fluid, the length of the capillary slot in axial direction of the main tubing exceeding the maximum contact length of a segmentation element in this direction.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings represent by way of example several embodiments of the apparatus according to the invention.

FIG. 1 is a more or less diagrammatic view of a known laboratory equipment in which the new method and apparatus for the separation of segmentation elements is used,

FIG. 2 shows a diagrammatic longitudinal section through a simple embodiment of the new apparatus, illustrating the principle of its operation,

FIG. 3 is the corresponding cross-sectional view taken along the line A-A of FIG. 2,

FIG. 4 is a longitudinal section through a modified embodiment of the new apparatus, in a diagrammatic representation,

FIG. 5 is a longitudinal section through the new apparatus combined into one unit with the flow cell of a measuring instrument, the section being taken along the line B--B of FIG.

FIG. 6 is a cross-sectional view of the apparatus shown in FIG. 5 and taken along the line C-C of FIG. 5,

FIG. 7 shows a longitudinal sectional view of the new apparatus of a simple design, enabling an easy manufacture thereof,

FIG. 8 is the corresponding cross-sectional view, taken along the line D-D of FIG. 7.

FIG. 9 shows another embodiment of the apparatus in a longitudinal section,

FIG. 10 is the corresponding cross-sectional view taken along the line EE from FIG. 9,

FIG. 11 illustrates a further modification ,of the apparatus,

FIG. 12 is the corresponding cross-sectional view,

FIG. 13 shows the new apparatus combined with a flow cell in a longitudinal section therethrough,

FIG. 14 a modified embodiment of the apparatus as combined with a flow cell, in a longitudinal sectional view.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, FIG. 1 represents diagrammatically an example of a laboratory appliance employing the apparatus according to the invention. It has to be noted that this appliance is not the subject of the present invention, it being disclosed only for the purpose of assisting in a clear understanding thereof. Further it has to be pointed out, that the invention can be used in a great variety of combinations and in connection with various appliances serving numerous purposes and that the disclosure of this particular example of use should under no circumstances be considered as limiting the scope of the inventive idea.

FIG. 1 represents by way of example a chromatographic column 1, which through a piping 2 supplies a pump 3 with a continuous stream of eluate, carrying components, such as amino acids, separated by the chromatographic action of the column. This stream will hereinafter be termed stream of the main fluid. The main fluid (i.e., the eluate with components distributed therein in a definite pattern), has to be measured, for instance by colorimetric means. If no provision were made, it would happen that along the relatively long path which the main fluid has to traverse, before reaching the colorimeter, the individual separated components would to a certain extend interrningle again, so that the result of the separation of the components achieved by the chromatographic process and therefore also the result of the analysis would be greatly distorted.

This is why the stream of the main fluid is segmented, which means that so-called segmentation elements are introduced into it (preferably at predetermined spacings), said segmentation elements consisting of bubbles of gas or drops of liquid, which are substantially immiscible with the main fluid. The stream of the main fluid is thereby divided into individual segments, which can then traverse even a fairly long pipeline, without the contents of the individual segments becoming intermingled to an undesirable degree. This ensures that the measuring instrument is supplied with the main fluid, in which the various components are distributed substantially in the same pattern in which they left the chromatographic column. In other words, the degradation of concentration gradients, which would be unavoidable, if the stream of main fluid were not segmented, is thereby to a high degree eliminated.

The segmentation elements are introduced into the stream of main fluid at required spacings by an apparatus, sometimes called bubbler and marked in the example shown by the reference numeral 4, said bubbler being connected to a discharge pipe 5 of the pump 3. A gas (air, nitrogen or the like) is admitted into the bubbler 4 through a pipe 6 from a source 7, or, if air is used as the segmentation medium, directly from the atmosphere. Alternatively the bubbler 4' can be arranged immediately below the chromatographic column and in this case the pipe 6' leads from the pump 3 to the bubbler 4, as shown in dotted lines in FIG. 1. The bubbler is a device well known in the art and will therefore not be described in detail. Instead of a gas it is of course possible to introduce into the stream of the main fluid a segmentation liquid, such as mercury, oil or the like, in the form of drops, which are likewise introduced into the main fluid stream by a known device similar to the bubbler 4.

The segmented stream of the main fluid proceeds from the bubbler 4 through a pipe 8 to a heating bath 9, in which it is heated in a coil 10 to the required temperature.

Before the stream of the main fluid is admitted to the measuring instrument, it has to be freed from the segmentation elements whichas said aboveconsist of a segmentation medium differing from the main fluid to be measured. The presence of this segmentation medium in the measuring instrument would interfere with its operation and lead to incorrect results.

The segmentation elements are eliminated from the stream of main fluid by a method forming the subject of the present invention and for performing the method an apparatus is used, which forms likewise a part of the present invention and is marked generally with the reference numeral II in FIG. I. The method as well as the apparatus for the elimination of segmentation elements according to the invention will be described in detail here below.

The segmented main fluid is admitted into the apparatus 11 through a tubing 12. The apparatus 11 is provided on the one hand with a tubing 13 leading to the drain or to a place of further treatment and, on the other hand, with a tubing 14 (which hereinafter will be called branch line), connected to a measuring instrument, in the present example a colorimeter 15. The latter is connected to a recorder 16, serving to record the results of the measurement. A flow cell (not shown in FIG. 1) of the colorimeter 15 is attached to a takeoff tube 17, which in the example shown leads to a suction pump 18 forming preferably one unit with the pump 3. The discharge side of the pump 18 is provided with a pipe 19 leading to the waste.

In a preferred embodiment the pump 3 is of the so-called peristaltic type. Such pump conveys a liquid, contained between resilient walls of a rubber tube or diaphragm, by a successive compression of said resilient walls by means of pressure members, such as a system of rollers rolling forward along the outside of the resilient wall, thereby forcing forward the medium enclosed between the resilient walls. The operation of the peristaltic pump 3 and the bubbler 4 can be synchronized in any suitable way, to make the bubbler 4 inject the segmentation elements in accordance with the individual batches of liquid, supplied by the pump 3.

The operation of the device shown in FIG. 1 may be already clear from the preceding description, but for the sake of completeness it will be summed up as follows:

A continuous stream of the main fluid emerging from the chromatographic column 1 is dosed by the pump 3 into the bubbler 4, where it is segmented by the injection of gas bubbles (or drops of liquid), forming segmentation elements. The segmented stream proceeds through the heating bath 9 to the apparatus 11 serving for the elimination of segmentation elements; a continuous stream of the main fluid is taken off the apparatus 11 through the branch line 14 and fed to the colorimeter 15, where it is measured and the result recorded in the recorder 16. The segmentation medium, together with the remainder of main fluid, proceeds to the tubing 13 either to further treatment or to the waste. The main fluid is taken off by the pump 18 through the flow cell of the colorimeter l5 and, after the measurement has been effected, it advances through the tube 17 and pump 18 to the waste pipe 19.

FIGS. 2 to 14 illustrate embodiments of the apparatus according to the invention. As shown in FIG. 2, the apparatus 11 is supplied with a stream of the main fluid 21, segmented by elements 22, which advances through a main tubing 23 in the direction of the arrow M. Provided in the main tubing 23 is a capillary slot 24, which is connected either directly or via a relatively small collecting space 25 to a branch line 26 (corresponding to the branch line 14 in FIG. 1), which is connected to a source of suction either directly or through a measuring instrument, as shown in FIG. 1, where the source of suction is represented by the suction pump 18.

The element 22 contacts the wall of the main tubing 23 in axial direction along a length, marked L in FIG. 2. This length is called contact length throughout this specification.

The length of the slot 24, in the flow direction of the segmented stream, exceeds the maximum contact length of a segmentation element in this direction. The width of the slot 24 has capillary dimensions, which means that its dimensions are such as to produce capillary effects between the segmentation medium (elements) and the material of the main tubing 23, said effects being usually described as capillary ascension and capillary depression.

The apparatus described operates as follows:

The segmented stream of the main fluid advances through the main tubing 23 along the capillary slot 24. As long as the slot 24 is in contact with the main fluid 21, the latter is sucked (or conveyed by another action) through this slot into the collecting space 25 and further through the branch line 26 for further use. If a segmentation element 22 comes into contact with the slot 24, it does not pass through the slot 24, but proceeds further through the main tubing 23 in the direction of the arrow M for the following reasons:

A segmentation element 22 is actually a bubble of a gas or a drop of a liquid enclosed in another medium, with which it does not mix; the surface of the bubble or drop shows a surface tension on the curved surface, the resulting force being directed towards the interior of the bubble and tending to shape it into a ball of the smallest volume. If no outer influences acted on the bubble, this surface tension would prevent any deformation of the bubble, which therefore would be unable to penetrate through the capillary slot 24, whose lateral (capillary) dimension is far smaller than the diameter of the bubble.

The bubble could pass through the capillary slot 24 only then, if the combined effect of all outer influences, to which the bubble is subjected, would overcome the resistance resulting from its surface tension and capillary forces acting against deformation to a dimension equaling the width of the capillary slot. Only in this case would the bubble be forced into and through the slot 24. The bubble is subject particularly to the hydrodynamic pressure occuring during the flow of the fluid, hydrostatic pressure of the fluid, which causes the flow, further to the capillary effect of the slot 24 and further to the take off (suction) effect in the slot 24, produced by the takeoff branch line 26. A decisive part plays further the surface affinity of the segmentation medium to the material of the tubing 23 in which the slot 24 is provided.

According to the invention this combined effect of the outer influences acting on the bubble is maintained at a value lower than the resistance of the capillary forces and surface tension of the bubble against deformation to a dimension equaling the width of the capillary slot 24 (so-called critical resistance against deformation"). In this way the entry of bubbles (or drops) of the segmentation medium through the slot 24 and thereby to the branch line 26 is positively avoided, so that it is only the main fluid that flows in a continuous stream through the branch line 26.

These outer influences are controlled by the regulation of pressures under which the segmented stream is passed through the main tubing 23, further by the take off forces in the branch line 26 and, in particular, by the dimension of the slot 24 in transverse direction, which has a decisive influence on its capillary effect. This dimension is chosen according to given conditions and, as mentioned above, depends to a considerable degree on the character of the materials used (segmentation medium and material of the wall in which the slot 24 is arranged).

Under the effect of outer pressures to which the segmentation element is subject, the boundary or outer surface of the segmentation element penetrates slightly into the slot 24, in which it assumes a considerable curvature (meniscus) in transverse direction, as indicated by 27 in FIG. 3; however, the element does not pass through the slot 24, but advances further through the main tubing 23 in the direction of the arrow M.

In order to take off the main fluid from one single or not more than two adjacent segments of the main fluid, the length of the slot 24 is chosen such, as to exceed the maximum contact length of a segmentation element, but shorter than, or equal to, the distance between the removed surfaces of two neighboring elements.

The main fluid will be taken off through the slot 24 under all circumstances without running the risk, that the segmentation element could interrupt the flow of main fluid into the slot. From FIG. 2 it is also evident that the main fluid will flow into the slot 24 either from a single or from not more than two adjacent segments, with the result that contamination by the contents of a greater number of segments is practically eliminated but not from an indefinite number of segmentswhich danger occurs in the known debubblers.

In some cases, where accuracy is not the primary consideration, and where emphasis is placed on a certain degree of smoothing or levelling the difl'erences in quality of the individual segments or on a high flow rate of the main fluid, the slot 24 may be extended over a number of segments of the main fluid, so that the latter is taken off from a greater number of segments simultaneously. This results, of course, in a levelling effect on the concentration gradients etc., and smoothing in a certain degree the resulting record line.

The area of the slot 24 or the collecting space 25 is so small, that the stagnation of the liquid occuring therein and therefore the undesirable mixing, are completely negligible and practically do not influence the accuracy of measuring at all.

In a practical embodiment the diameter of the main tubing may be e.g., 1 mm. or less and the transverse dimension of the capillary slot 0,3 to 0,5 mm. If the diameter of the main tubing is larger, the transverse dimension of the slot 24 may be larger as well, such as 1 mm., which is sometimes preferable for technological reasons.

FIG. 4 represents a modified embodiment of the new apparatus. The capillary slot in this case consists of a plurality of partial channels 28, opening into a main tubing 29 through capillary openings 30. The channels 28 communicate with a collecting conduit or space 31, attached through a branch pipe 32 to a source of suction. The total length of the system of partial channels 28 in the direction of the axis of the main tubing 29 is larger than the maximum contact length of a segmentation element 33 and preferably smaller than, or equal to, the distance between the remote surfaces of two neighboring elements. If necessary, however, this dimension can be even larger for reasons indicated in connection with the embodiments shown in FIGS. 2 and 3.

Under the influence of outer pressures, the outer surface of the segmentation elements 33 is pressed slightly into the openings 30 of channels 28, where it becomes considerably curved, both in a plane perpendicular to the axis of the main tubing as well as in a plane containing this axis, but it does not penetrate through the partial channels and advances further through the main tubing in the direction of the arrow N.

In the embodiments according to FIGS. 2 and 3, as well as FIG. 4 a considerable portion of the main fluid may be taken ofl from the main tubing 23 or 29 during the passage of the various segments over the slot 24 or channels 28, so that in the main tubing 23 or 29 there may remain a small residuum of the main medium, for instance not more than 10 percent, between the various elements of the segmentation medium (which of course has not been withdrawn into the branch line).

The main fluid can be fed into the branch line 26 or 32 either by the effect of suction produced by a suction pump (as indicated in FIG. 1 or in any other suitable way.

FIGS. 5 and 6 show a practical embodiment of the new apparatus in combination with a flow cell. In a block 34, with an attachment 35, made e.g., of transparent organic glass or any other suitable material, the main tubing is produced by a boring 36 (see particularly FIG. 6). Attached to the boring 36 at one side is a supply tubing 37 and at the other side a discharge tubing 38. A capillary slot 39 is provided in the block 34 and, as near as possible to the slot 39 a flow cell 40 is arranged and covered from both sides with covers 41, 41' made of a transparent material. The capillary slot 39 communicates with the flow cell 40 over a channel 42, which is relatively short and opens to one side of the flow cell 40. The other side of the flow cell 40 communicates with a hollow needle 43, attached to the branch line for the takeofi.

The capillary slot 39 is rounded or tapered at its ends, in order to eliminate sharp comers, however slight, which might adversely affect and perhaps interfere with the operation of the apparatus.

The embodiment shown in FIGS. and 6 has the advantage that the stream of main fluid enters the flow cell 40 along a very short and narrow path, with the result that a possible degradation of the concentration gradients is restricted to a minimum (it has to be noted that in the slot 39 and channel 42 the main fluid is not segmented any more). The block 34 with the flow cell 40 is inserted in a measuring instrument of a known type, of which only the diaphragm 44,45 are shown for the sake of completeness.

FIGS. 7 and 8 show another simple embodiment of the new apparatus. The main tubing consists of a tube 46, in which a capillary slot 47 is cut. The tube 46 is inserted in the boring of a bushing 48. Coaxially attached to the tube 46 is a supply tube 49 and a discharge tube 50. Opposite the slot 47 and in open communication therewith is a hollow needle 51 arranged in the bushing 48 and connected to a takeoff device. The slot 47 is tapered at both ends of the tube 46 by inlays 52 of any suitable material, secured in these places and serving to eliminate any sharp corners.

FIGS. 9 and show another modification of the new apparatus. Cut in a tube 53 is a circular groove 54 extending diametrically through the tube, as shown in FIG. 9, so that at the point 55 there is produced a capillary slot of the desired shape, whose ends are already rounded. The portion 56 of the slot in the opposite wall of the tube 53 is closed by means of a seal 57, blending with the wall of the tube 53, which is inserted into the boring of a bushing 58. A hollow needle 59, attached to a takeoff device, is inserted in the bushing 58 opposite the slot 55 and in open communication therewith.

FIGS. 11 and 12 are illustrations of another simple arrangement. A slot 60 is cut in a tube 61 from one side only and inlays 62, 62' are fitted at both ends thereof, to impart the desired tapered or rounded shape to the slot 60, as indicated in FIG. 7. The tube 61 is then inserted into a boring in a block 63 housing a hollow needle 64, which communicates with the slot 60.

FIGS. 13 and 14 represent a combination of an apparatus, designed as above, with a flow cell into one unit, similar to the arrangement shown in FIGS. 5 and 6, the only difference being, that according to FIG. 13 a block 65 housing a flow cell 66 carries a block 67 corresponding substantially to the block 63 according to FIGS. 1 1 and 12, a tube 68 and a slot 69 being provided in the block 67. According to FIG. 14 the block 70, housing a flow cell 71, carries a cylindrical bushing corresponding substantially to the bushing 48 shown in FIGS. 7 and 8 or to the bushing 58 shown in FIGS. 9 and 10.

In an alternative embodiment of the invention it is possible to change the characteristics of the process in such a way that the tapped stream has not the form of a continuous stream (of main fluid) but likewise of a segmented stream. The conditions, i.e., pressures etc., are chosen such that in addition to the main fluid a part of the segmentation medium penetrates through the capillary slot, with the result, that in the branch line a segmented stream is obtained as well. This may be advantageous in some special cases.

I claim:

1. A method for withdrawing liquid samples from a stream flowing through tubing, said stream being divided into segments by fluid segmentation elements spaced apart from each other in the direction of flow of said stream, said method comprising:

conducting said stream across a discharge port in said tubcausing said fluid elements to contact the discharge port along a length of said port, said port having a length greater than the length of said elements;

causing said fluid elements to remain within said tubing by having the width of said discharge port less than the width of said elements;

said elements having a diameter as large as the internal diameter of said tubing and having an exterior film of sufficient tension to retain said fluid therein while passing across said port;

withdrawing a portion of said liquid within said port by applying a flow inducing pressure to said port without removing fluid from said elements; and

conducting the remaining portion of said stream with said segmentation elements therein in said flow direction downstream from said port.

2. The method according to claim 1 including subjecting said liquid to capillary action at said port, said segmentation elements having difi'erent fluid properties and being unaffected by said capillary action.

3. The method according to claim 1 including conducting liquid from said port to a chromatographic flow cell, whereby successive liquid segments of said stream pass continuously through said flow cell for analysis.

4. In apparatus for liquid chromatographic apparatus of the type including a chromatographic column, a tube for conducting a stream of eluate liquid from the column for analyzing the eluate liquid, and including a device for inserting fluid segmentation elements in said tube at intervals in said eluate stream to divide said stream into segments, said apparatus further including means for separating said eluate liquid from said elements and the remainder of said stream, said separating means comprising:

means forming a tubular passage for conducting the segmented fluid stream from an upstream region to a downstream region, said passage means having an impervious internal wall extending between said regions and defining a flow passage for said stream,

said wall having a port in communication with said tubular passage, said port having a length extending in the direction of flow through said passage, whereby said length of said port is greater than the length of said element, and having a width extending transverse to the direction of flow in said passage, whereby said port width is less than the width of said element said port length being greater than said port width, and a discharge conduit connected with said port for conducting eluate to said flow cell, whereby the length of the elements introduced into said eluate stream are shorter than the length of said port to allow eluate to be drawn into said discharge conduit while surface tension in said elements prevents entry of said element fluid into said discharge conduit and said elements move continuously from said upstream region to said downstream region while eluate liquid is withdrawn through said discharge conduit.

5. The apparatus according to claim 4 wherein the width of said port is of capillary size and is in the form of a continuous slot.

6. The apparatus according to claim 4 including chamber means between said port and said conduit for collecting said fluid.

7. The apparatus according to claim 5 including a plurality of bridge members extending transversely across said port, said bridge members being spaced apart from each other along the length of said port.

8. The apparatus according to claim 5 including chamber means between said port and said discharge conduit for collecting eluate fluid. 

2. The method according to claim 1 including subjecting said liquid to capillary action at said port, said segmentation elements having different fluid properties and being unaffected by said capillary action.
 3. The method according to claim 1 including conducting liquid from said port to a chromatographic flow cell, whereby successive liquid segments of said stream pass continuously through said flow cell for analysis.
 4. In apparatus for liquid chromatographic apparatus of the type including a chromatographic column, a tube for conducting a stream of eluate liquid from the column for analyzing the eluate liquid, and including a device for inserting fluid segmentation elements in said tube at intervals in said eluate stream to divide said stream into segments, said apparatus further including means for separating said eluate liquid from said elements and the remainder of said stream, said separating means comprising: means forming a tubular passage for conducting the segmented fluid stream from an upstream region to a downstream region, said passage means having an impervious internal wall extending between said regions and defining a flow passage for said stream, said wall having a port in communication with said tubular passage, said port having a length extending in the direction of flow through said passage, whereby said length of said port is greater thAn the length of said element, and having a width extending transverse to the direction of flow in said passage, whereby said port width is less than the width of said element said port length being greater than said port width, and a discharge conduit connected with said port for conducting eluate to said flow cell, whereby the length of the elements introduced into said eluate stream are shorter than the length of said port to allow eluate to be drawn into said discharge conduit while surface tension in said elements prevents entry of said element fluid into said discharge conduit and said elements move continuously from said upstream region to said downstream region while eluate liquid is withdrawn through said discharge conduit.
 5. The apparatus according to claim 4 wherein the width of said port is of capillary size and is in the form of a continuous slot.
 6. The apparatus according to claim 4 including chamber means between said port and said conduit for collecting said fluid.
 7. The apparatus according to claim 5 including a plurality of bridge members extending transversely across said port, said bridge members being spaced apart from each other along the length of said port.
 8. The apparatus according to claim 5 including chamber means between said port and said discharge conduit for collecting eluate fluid. 